1. Field of the Invention
This invention relates to a water-resistant, moisture permeable film and to a flexible, laminated product made with a layer or layers of the film and a textile material. The product is suitable for making water-resistant garments, tarpaulins, tents, and the like. More particularly, the present invention relates to a polyamide film with a permeability of at least 0.0008 metric perm-cm. when tested at 20.degree. C. and 65 percent relative humidity and of at least 0.0006 metric perm-cm. when tested at 30.degree. C. and 50 percent relative humidity. These films are suitable for lamination to a polyamide material to render the same water-resistant and moisture permeable.
2. The Prior Art
Layered articles or products which are waterproof, moisture permeable, and flexible are well known in the art. See, e.g., U.S. Pat. Nos. 4,493,870 to Vrouenraets et al., 4,443,511 to Worden et al., and 4,194,041 to Gore et al., all of which are hereby incorporated by reference. These products, which may be used to make fabrics to protect humans from wet weather, are formed of a hydrophilic layer covered with a hydrophobic layer.
The hydrophilic layer may be a textile material layer as in U.S. Pat. No. 4,493,870 or films of polyurethane polymer/perfluorosulfonic acid product as in U.S. Pat. No. 4,194,041.
The preferred hydrophobic layer of U.S. Pat. No. 4,194,041 is made of expanded polytetrafluoroethylene (PTFE) film. See U.S. Pat. No. 3,953,566 to Gore et al., hereby incorporated by reference, for preparation of these films. The preferred hydrophobic layer of U.S. Pat. No. 4,493,870 is a film of a copolyether ester consisting of a plurality of recurrent intralinear long-chain ester units and short-chain ester units which are randomly joined head-to-tail through ester bonds.
The key to these products is that the materials used prevent leakage of water into the article when fabricated while permitting transmission of moisture to the outside of the article. While the hydrophobic films of the prior art do this, they are relatively expensive; this led to development of the hydrophilic film of the present invention. Under certain test conditions, this film is more moisture permeable (breathable) than the films suggested by U.S. Pat. No. 4,493,870, while retaining impermeability to liquid water.
The block copolymer from which the films of the present invention are made have been used to form hydrophilic nylon fibers, as disclosed in the article "Hydrophilic Nylon for Improved Apparel Comfort" by R. A. Lofquist et al., published in Textile Research Journal Volume 55, no. 6, pages 325-333 June of 1985, hereby incorporated by reference.